I just bought a 2007 Taco with TPMS. Light came on last week the result of one tire being a little low on pressure. No problem - I topped up the pressure and the light went away. All is good. The strange thing is that I just put a set of steel rims and snow tires on the truck and fully expected to suffer through having to look at the TPMS light for the winter, but the TPMS light hasn't come on. I'm not complaining. This is great but I can't understand why it hasn't come on. I'm sure the tire dealer didn't install TPMS in the winter rims. Any ideas out there.

I have two sets of tires/rims...one for summer & one for winter.
I only have tpms in my winter tires (truck came stock with steel rims & steel rim tpms sensors)
My summer tires/rims are oem TRD OR alloys and no sensors.
I do not get a light either.
It does trigger if I drive out of a certain range of my stored winter tires (in the garage). It is pretty far.
Around town, at work all day 20 miles away no light at all.
If I drive out around 30 miles it goes off but...
once home and parked overnight in the driveway...the light resets on its own.

It has been this way for 3 seasons and did the same for my tundra before that.

Once the system did trigger in the summer only to let me know that the tires in storage were low.

When I am on a longer trip, I just put a business card over the light until I get home.

Interesting I didn't think the sensors would work over more than a couple feet.

yeah I thought it is weird too but hey it works for me.
I do not know if it a time to live TTL/handshake acknowledgement from the sensor to the ecu & back, but was surprised at the distance or combo time/distance.
Regardless whatever it is, the main thing is 99% of the time I do not get a light without having sensors in the other set of tires/rims. Others have had the same experience as well.
My truck is a 2006 & has a sensor in the spare.
No sure if that makes a diff. The OP does too.